ISSN:0009-7330    

出版商:OVID    

年代:1999

数据来源: OVID

ISSN:0009-7330    

出版商:OVID    

年代:1999

数据来源: OVID

摘要:

cAMP and cGMP are known to suppress vascular smooth muscle cell (SMC) proliferation. In this study, our aim was to delineate the molecular mechanism underlying cAMP and cGMP suppression of cell cycle transition in human SMCs. cAMP inhibits both platelet-derived growth factor–stimulated cyclin-dependent kinase (cdk) 2 and cdk4 activation through upregulation of the cdk2 inhibitor p27Kip1and downregulation of cyclin D1 expression, which leads to a complete arrest of the cells in phase G1. In contrast, cGMP inhibits cyclin D1 expression, inhibits cdk4 activation, and delays platelet-derived growth factor–mediated cdk2 activation, resulting in a delay in G1/S transition. A transient increase in p27Kip1in cdk2 immunoprecipitates, without changes in total cellular p27Kip1levels, correlates with the delay in cdk2 activation caused by cGMP. Thus, cAMP and cGMP differentially affect cell cycle through distinct regulation of cell cycle molecules in human SMCs.

ISSN:0009-7330    

出版商:OVID    

年代:1999

数据来源: OVID

摘要:

Vascular endothelial growth factor (VEGF) is a key modulator of angiogenesis during development and in adult tissues, whereas the related VEGF-C has been shown to induce both lymphangiogenesis and angiogenesis. To better understand the specific functions of these growth factors, we have here analyzed their binding to sections of mouse embryonic and adult tissues and compared the distribution of the bound growth factors with the expression patterns of the 3 known members of the VEGF receptor family as well as with neuropilin-1, a coreceptor for VEGF165. Partially overlapping patterns of VEGF and VEGF-C binding were obtained in embryonic tissues, consistent with the expression of all known VEGF receptors by vascular endothelial cells. However, the most striking differences of binding were observed in the developing and adult heart, in which VEGF decorated all vessels, whereas strong VEGF-C signals were obtained only from epicardial vessels. In the lymph nodes, VEGF and VEGF-C showed distinct binding patterns in agreement with the differential location of their specific receptors. These results show that both VEGF-C and VEGF target embryonic blood vessels, whereas a more selective binding of VEGF-C occurs to its lymphatic vascular receptor in certain adult tissues. Our results suggest that VEGF and VEGF-C have both overlapping and distinct activities via their endothelial receptors.

ISSN:0009-7330    

出版商:OVID    

年代:1999

数据来源: OVID

摘要:

The sphingolipid metabolites, sphingosine (SPH), SPH 1-phosphate (S1P), and sphingosylphosphorylcholine (SPC), can act as intracellular as well as extracellular signaling molecules. These compounds have been implicated in the regulation of cell growth, differentiation, and programmed cell death in nonmyocytes, but the effects of sphingolipid metabolites in cardiac myocytes are not known. Cultured neonatal rat cardiac myocytes were stimulated with SPH (1 to 10 &mgr;mol/L), S1P (1 to 10 &mgr;mol/L), or SPC (0.1 to 10 &mgr;mol/L) for 24 hours to determine the effects of sphingolipid metabolites on the rates of protein synthesis and degradation. Stimulation with SPC led to an increase in the total amount of protein, an accelerated rate of total protein synthesis, and a decrease in protein degradation in a dose-dependent manner. However, S1P had little effect and SPH had no effect on total protein synthesis. In addition, stimulation with SPC led to a 1.4-fold increase in myocardial cell size and enhanced atrial natriuretic factor gene expression. Pretreatment of the cardiac myocytes with pertussis toxin or PD98059 attenuated the SPC-induced hypertrophic growth response. Further, stimulation with SPC increased phosphorylation of mitogen-activated protein kinase (MAPK) and stimulated MAPK enzyme activity. Finally, endothelin-1 stimulated the generation of SPC in cardiac myocytes. The observation that SPC induces a hypertrophic growth response in cardiac myocytes suggests that SPC may play a critical role in the development of cardiac hypertrophy. The effects of SPC could be mediated, in part, by activation of a G protein–coupled receptor and a MAPK signaling cascade.

ISSN:0009-7330    

出版商:OVID    

年代:1999

数据来源: OVID

摘要:

Three-dimensional cardiac mapping in rabbits with nonischemic cardiomyopathy has shown that ventricular arrhythmias initiate by a nonreentrant mechanism that may be due to triggered activity from delayed afterdepolarizations. Delayed afterdepolarizations are thought to be due to spontaneous release of Ca2+from the sarcoplasmic reticulum (SR) and consequent activation of an inward Na+/Ca2+exchange (NaCaX) current. The goal of this study was to determine whether there is enhanced NaCaX gene expression and functional activity that may contribute to nonreentrant activation. Heart failure (HF) was induced in rabbits by combined aortic insufficiency and aortic constriction. HF rabbits had left ventricular enlargement (left ventricular end-diastolic dimension increased from 1.43±0.03 to 1.97±0.05 cm) and severely depressed function (fractional shortening reduced from 37% to 26%,P<0.02). Heart-to-body weight was increased by 79% in HF. Western blots showed a 93% increase in NaCaX protein in HF (P<0.04). NaCaX mRNA (7-kb transcript) was increased by 104% relative to the 18S rRNA in HF. A 14-kb NaCaX transcript was also seen in the HF rabbits, raising total NaCaX mRNA to 2.7-fold compared with controls. The amplitude of caffeine-induced contractures, used to assess SR Ca2+load, was not significantly different in HF. Relaxation and [Ca2+]idecline during caffeine-induced contractures is attributable to Ca2+transport by NaCaX and was 61% and 45% faster in HF (P<0.05), respectively. NaCaX current measured under controlled voltage clamp conditions was also 2-fold higher in HF cells. SR Ca2+-ATPase mRNA and protein levels and Ca2+current density were not significantly altered in HF. Twitch amplitudes from HF myocytes were 26% smaller compared with control (P<0.02), but twitch relaxation and [Ca2+]idecline (due largely to SR Ca2+-ATPase) were not altered. Thus myocytes and myocardium from HF rabbits exhibit enhanced NaCaX expression and function. The enhanced NaCaX activity may contribute to depressed contractions, increased transient inward current (for a given SR Ca2+release), delayed afterdepolarizations, and nonreentrant initiation of ventricular tachycardia in this arrhythmogenic model of HF.

ISSN:0009-7330    

出版商:OVID    

年代:1999

数据来源: OVID

摘要:

Recent studies have postulated the contribution of nitric oxide (NO) released by the endothelium to the beneficial effects of estrogen. Despite a neuronal-type NO synthase (nNOS) described in neutrophils, less is known about the effect of estrogen in these cells. The aim of the present study was to analyze the expression of nNOS protein in human neutrophils under different estrogenic conditions. We first analyzed nNOS expression in neutrophils obtained from premenopausal women. During the first 2 days of the follicular phase (low circulating estrogen concentrations), nNOS expression in neutrophils was reduced with respect to that found in neutrophils obtained from the same donors during the ovulatory phase (high circulating estrogen concentrations). Moreover, the expression of nNOS protein in neutrophils obtained from postmenopausal women after transdermal estrogen therapy was markedly enhanced with respect to that observed before the treatment. In vitro incubation of neutrophils derived from men for 6 hours with 17&bgr;-estradiol (10−10to 10−8mol/L) upregulated the expression of nNOS protein. The 17&bgr;-estradiol receptor antagonists, tamoxifen (10−8mol/L) and ICI 182780 (10−8mol/L), inhibited the upregulation of nNOS protein induced by 17&bgr;-estradiol. The putative functional implication was denoted by a reduced expression of the CD18 antigen on the surface of 17&bgr;-estradiol–incubated neutrophils, which was accompanied by a decreased adhesive capacity. Both effects were prevented by an NO antagonist. In conclusion, the in vivo levels of circulating estrogen concentrations seem to be associated with the level of nNOS protein expression in neutrophils from women. Moreover, low doses of 17&bgr;-estradiol upregulate nNOS protein expression in neutrophils from men. The increased ability of 17&bgr;-estradiol–incubated neutrophils derived from men to produce NO reduced their adhesive properties.

ISSN:0009-7330    

出版商:OVID    

年代:1999

数据来源: OVID

摘要:

The redox state of the heme of soluble guanylate cyclase (sGC) may regulate the sensitivity of vascular tissue to nitric oxide (NO). In this study, diphenyliodonium (DPI) is used as an inhibitor of flavoprotein oxidoreductases to examine their potential role in the expression of NO-elicited cGMP-associated arterial relaxation and sGC stimulation. The relaxation of endothelium-removed bovine coronary arteries (BCAs) precontracted with 30 mmol/L KCl to the NO donorS-nitroso-N-acetyl-penicillamine (SNAP) or to NO is markedly suppressed by 10 &mgr;mol/L DPI under an atmosphere of 21% O2(5% CO2). In contrast, DPI has minimal effects on the relaxation to SNAP under 95% N2(5% CO2). If BCAs are treated with DPI under 21% O2and then exposed to the hemoprotein reductant sodium dithionite (1 mmol/L) under N2, there is a partial reversal of the inhibitory effects of DPI compared with BCAs that were not treated with dithionite. DPI did not inhibit relaxation elicited by 8-bromo-cGMP or forskolin. Increases in tissue cGMP levels stimulated by SNAP were eliminated by pretreatment of BCAs with DPI under 21% O2but not under N2. Activation of sGC by SNAP in BCA homogenate was also eliminated when vessels were pretreated with 10 &mgr;mol/L DPI under 21% O2, but DPI did not have an inhibitory effect when directly added to the assay of sGC activity. These observations are consistent with a flavoprotein-dependent oxidoreductase functioning to prevent the expression of a novel O2-dependent process from oxidizing the heme on sGC and inhibiting NO-elicited cGMP-mediated BCA relaxation.

ISSN:0009-7330    

出版商:OVID    

年代:1999

数据来源: OVID

摘要:

Smooth muscle cell (SMC) proliferation that results in neointima formation is implicated in the pathogenesis of atherosclerotic plaques and accounts for the high rates of restenosis that occur after percutaneous transluminal coronary angioplasty, a widespread treatment for coronary artery disease. Endothelial lesions trigger intense proliferative signals to the SMCs of the subintima, stimulating their reentry into the cell cycle from a resting G0state, resulting in neointima formation and vascular occlusion. Cellular proliferation is negatively controlled by growth-regulatory or tumor-suppressor genes, or both, such as the retinoblastoma gene family members (RB/p105, p107, RB2/p130). In the present study, we show thatRB2/p130inhibited SMC proliferation in vitro and in vivo. We used the rat carotid artery model of restenosis to demonstrate that adenovirus-mediated localized arterial transduction ofRB2/p130at the time of angioplasty significantly reduced neointimal hyperplasia and prevented restenosis. Furthermore, the ability of pRb2/p130 to block proliferation correlated with its ability to bind and sequester the E2F family of transcription factors, which are important mediators of cell cycle progression. These results imply thatRB2/p130could be an important target for vascular gene therapy.

ISSN:0009-7330    

出版商:OVID    

年代:1999

数据来源: OVID

摘要:

Insulin-like growth factor-I (IGF-I) is a potent stimulant of smooth muscle cell (SMC) migration and proliferation and has been implicated in the development of experimental atherosclerotic lesions. Because optimal stimulation of SMC in vitro by IGF-I requires ligand occupancy of &agr;V&bgr;3, these studies were conducted to determine whether &agr;V&bgr;3 antagonists would result in a change in lesion size and whether they could alter IGF-I-mediated actions. Clamps were placed on the carotid and femoral arteries of normal pigs that had been fed a high-cholesterol diet for 4 weeks. &agr;V&bgr;3 inhibitors (SC-69000, SC-65811) (10−6mol/L) or saline were infused for 2 weeks into the peristenotic area. Lesion area, the number of SMC layers, and proliferating cell nuclear antigen positive cells were determined in a 1.2-mm segment of each artery. Lesion areas were 304 788±113 453 &mgr;2(saline), compared with 149 799±35 456 &mgr;2(SC-69000) (P<0.01). Lesion areas in arteries treated with SC-64258, a compound that does not bind to &agr;V&bgr;3, were 310 284±160 467 &mgr;2,P=not significant. In a second experiment, lesion areas were 110 391±17 347 &mgr;2(saline) and 59 533±17 568 &mgr;2(SC-65811,P<0.001). Neointimal SMC layers were reduced by SC-65811 from 7.4±4.5 to 3.0±0.4 (P<0.001). To determine whether IGF-I action was altered, IGF binding protein-5, which is synthesized in response to IGF-I, was analyzed. IGF-I binding protein-5 mRNA abundance was reduced by 67±8% in the 6 lesions treated with SRL-69000 compared with saline controls (P<0.001). We conclude that &agr;V&bgr;3 antagonists block the development of lesions in pigs that have been induced by a high-cholesterol diet and stenosis, and the effect of these compounds is associated with their ability to inhibit IGF-I–mediated signaling.

ISSN:0009-7330    

出版商:OVID    

年代:1999

数据来源: OVID